miR-181a Promotes Multiple Protumorigenic Functions by Targeting TGFβR3

Cutaneous squamous cell carcinoma (cSCC) comprises 15.20% of all skin cancers and has a well-defined progression sequence from precancerous actinic keratosis to invasive cSCC. To identify targets for chemoprevention, we previously reported a cross-species analysis to identify the transcriptional drivers of cSCC development and identified miR-181a as a potential oncomiR. We show that the upregulation of miR-181a promotes multiple protumorigenic properties by targeting an understudied component of TGF beta signaling, TGF beta R3. miR-181a and TGF beta R3 are upregulated and downregulated, respectively, in cSCC. miR-181a overexpression (OE) and TGF beta R3 knockdown (KD) significantly suppresses UV-induced apoptosis in HaCaT cells and in primary normal human epidermal keratinocytes. In addition, OE of miR-181a or KD of TGF beta R3 by short hairpin RNA enhances anchorage-independent survival. miR-181a OE or TGF beta R3 KD enhances cellular migration and invasion and upregulation of epithelial.mesenchymal transition markers. Luciferase reporter assays demonstrate that miR-181a directly targets the 30-untranslated region of TGF beta R3. miR-181a upregulates phosphorylated SMAD3 levels after TGF beta 2 administration and results in elevated SNAIL and SLUG expression. Finally, we confirm in vivo that miR-181a inhibition compromises tumor growth. Importantly, these phenotypes can be reversed with TGF beta R3 OE or KD in the context of miR-181a OE or KD, respectively, further highlighting the physiologic relevance of this regulation in cSCC.

Automated summary

Upregulation of miR-181a promotes the development of cutaneous squamous cell carcinoma (cSCC) by targeting TGF beta R3, a component of TGF beta signaling. Overexpression of miR-181a or knockdown of TGF beta R3 significantly suppresses UV-induced apoptosis in HaCaT cells and normal human epidermal keratinocytes. Moreover, miR-181a overexpression or TGF beta R3 knockdown enhances the survival, migration, and invasion of tumor cells.